[Indications and instructions to patients for a positron emission tomography-PET scan. The importance of the hybridic PET/CT-computerised tomography scan and which specialty should be responsible for its function].

Indications and instructions to patients for performing a positron emission tomography - PET scan are mentioned. Although PET camera was developed in 1970 its clinical indications were established in about 1998. The hybridic PET/CT- computerized tomography scanner appeared in 2001 and its clinical indications are still under discussion. These discussions refer to both the use of PET/CT as an acquisition correction and anatomic localization device for PET images (AC/A) and to its use as a diagnostic CT scan (dCT). Most of the patients submitted for a PET scan have already done a dCT scan. This was the case in 286 out of the first 300 patients referred to "Evangelismos" hospital in Athens for a PET scan. These two scans can be matched electronically. Extra cost, space, personnel and radiation absorption dose especially in children, are additional factors to be considered in using the PET/CT scanner. The specialty of Nuclear Medicine is now based on the PET camera, its best part and main equipment for molecular imaging. It is very much easier and faster for a Nuclear Medicine physician who routinely reports tomographic PET and SPET images, to be familiar with the CT images than for a Radiologist to get to "know how" about the PET camera and the whole Nuclear Medicine Department. Nuclear Medicine is about open radiation sources, molecular imaging, specific radio-pharmacology, radiobiology, radiation protection etc, while on the other hand in some countries, Nuclear Physicians have already spent, as part of their official training, six months in a Radiology Department whose function is considered to be at least 25% about the CT scanner. We come to the conclusion that the PET/CT scanner should be under the responsibility of the Nuclear Medicine Department and the Radiologist should act as an advisor.

Comparative evaluation of 99mTc-depreotide and 201Tl chloride single photon emission tomography in the characterization of pulmonary lesions.

PURPOSE: To compare (99m)Tc-depreotide and (201)Tl chloride SPET in the characterization of pulmonary lesions. METHODS: Fifty-seven pulmonary lesions from 33 patients suspected of malignancy in computed tomography, were assessed by (99m)Tc-depreotide and (201)Tl early and delayed SPET imaging. Images were visually assessed and the tumour-to-normal (T/N) lung activity ratio for early (ER) and delayed (DR) scans and the retention index (RI), were calculated in every lesion. A final diagnosis was reached for all lesions, based either on histology or prolonged clinical and radiological follow-up. RESULTS: Twenty-three lesions were characterized as malignant and 34 benign. In visual analysis, all malignant lesions accumulated both tracers resulting in sensitivity and negative predictive values of 100%. However, false positive interpretations resulted in a specificity of 64.7% and 67.6% for (99m)Tc-depreotide and (201)Tl, respectively. ER and DR of both agents and the RI of (99m)Tc-depreotide were significantly higher in malignant, compared to benign lesions. In defining thresholds of abnormality from ROC analysis, a significant increase in specificity was observed for both tracers in both scan phases (91.2% for all), as compared to visual analysis (P<0.01). There was no significant difference in the diagnostic performance between (99m)Tc-depreotide DR and (201)Tl DR, although the former provided the highest T/N ratio. CONCLUSION: This study demonstrates that (99m)Tc-depreotide and (201)Tl SPET are equally effective and may be useful in the non-invasive determination of lung malignancy. The specificity of both techniques is significantly improved by quantifying radiopharmaceutical accumulation in pulmonary lesions.

The contribution of conventional nuclear molecular imaging in characterising the nature of a growing solitary pulmonary nodule. Report of a case.

The solitary pulmonary nodule (SPN) is a relatively common imaging finding, often representing a diagnostic challenge. Radiological appearance, growth rate calculation during follow up and probability of malignancy assessment by the Bayes' theorem are widely used for identifying the nature of a SPN. Molecular imaging by fluoro-18 deoxy glucose positron emission tomography has revolutionised non-invasive diagnosis of lung cancer, but the low-cost, widely available conventional nuclear imaging modalities still remain valid in the field. We present a case of a growing SPN in a middle-aged male smoker. Growth rate assessment by sequential computed tomography scans, over a follow up period of five years, was suggestive of benign histology, while Bayesian analysis warranted histological confirmation of the nodule's nature. Imaging by both labelled somatostatin analogue technetium 99m-depreotide ((99m)Tc-depreotide) and thallium 201-chloride was almost exclusive of malignancy. The nodule was excised and histology showed a pulmonary hamartoma. We briefly discuss the relative role of invasive and non-invasive methods, with emphasis in conventional radionuclide molecular imaging, for the identification of the nature of SPN.

Interhemispheric asymmetry in brain perfusion before and after carotid stenting: a 99mTc-HMPAO SPECT study.

PURPOSE: To assess the effect of unilateral carotid angioplasty and stenting (CAS) on cerebral perfusion asymmetry in patients with severe extracranial carotid stenosis by means of technetium Tc 99m hexamethyl-propyleneamine oxime brain single photon emission computed tomography ((99m)Tc-HMPAO SPECT). METHODS: Twenty-nine consecutive patients (22 men; median age 68 years, range 58-80; 13 symptomatic) undergoing unilateral CAS were included in the study. Brain perfusion was assessed by (99m)Tc-HMPAO brain SPECT prior to the procedure and postoperatively at 8 hours and at 2 to 4 months. The asymmetry index (AI), a measure of the interhemispheric asymmetry in perfusion, was calculated as [(counts in "healthy" hemisphere-counts in hemisphere with carotid stenosis)/counts in "healthy" hemisphere]x100. RESULTS: The preoperative AI demonstrated a wide variation (mean -0.5%+/-8.4%, range -19.5% to 14.1%). There was no significant correlation between the degree of carotid stenosis and preoperative AI. The mean preoperative AI in the asymptomatic patients was lower than in the symptomatic group [-4.0%+/-8.5% (range -19.5% to 8.2%) versus 3.8%+/-6.4% (range -5.2% to 14.1%), p=0.01], suggesting reduced perfusion of the ipsilateral cerebral hemisphere compared to the contralateral side in symptomatic patients. AI variation did not improve after CAS; there was no difference in AI among the 3 SPECT studies (p=0.75). Preoperative AI correlated significantly with late AI (r=0.74, p<0.0001); however, there was no statistically significant correlation between immediate postoperative AI and either preoperative (r=0.24, p=0.217) or late (r=0.24, p=0.249) AI. CONCLUSION: Asymmetry in cerebral perfusion in patients with severe extracranial carotid atherosclerosis does not correlate with the degree of carotid stenosis. Symptomatic patients demonstrate compromised perfusion of the ipsilateral hemisphere compared to asymptomatic patients. As judged by (99m)Tc-HMPAO SPECT scanning, cerebral perfusion patterns do not significantly change after CAS.

[Nuclear medicine procedures in lung cancer imaging]. / In Process Citation.

Lung cancer is nowadays one of the most common malignancies and the leading cause of cancer mortality worldwide. Its early diagnosis and treatment is therefore the target of extensive research. Although radiologic imaging methods, especially CT, are the most widely used, they have well known constraints, including solitary pulmonary nodule characterisation, mediastinal lymph node staging, characterisation of the remaining tissue after chemo- or radiotherapy and early diagnosis of relapse. The main reason for these drawbacks is that radiologic methods primarily rely upon morphologic and anatomic criteria, which usually have little relevance to the biological status of a pulmonary lesion. The radiopharmaceuticals used in nuclear medicine, exploit special pathophysiologic localization mechanisms and provide unique functional information for their target tissues. Thus, many of the above mentioned problems can be elucidated. This is obvious in the published figures of sensitivity and specificity of the radionuclidic methods, which are often superior to those of CT [Table 1: see text]. In this article the main nuclear medicine procedures in the field of lung cancer imaging are reviewed. Emphasis is given in newer developments such as (99m)Tc-sestamibi, labeled somatostatin analogues and positron emission tomography with (18)F-FDG. We especially describe the "weaknesses" of the anatomic-radiologic imaging modalities and how the attending physicians, i.e. the pneumonologists, oncologists and thoracic surgeons can overcome them, by using the functional imaging methods of nuclear medicine.